The invention relates to an electrical switch as claimed in the precharacterizing clause of patent claim 1, and to a switch arrangement comprising a plurality of electrical switches.
Electrical switches are used in motor vehicles, as control switches for switching the motor vehicle lighting, the windshield wipers, the rear windshield heating, the electric window winders, the internal central locking and other functions on and off. A number of such switches can be combined as control panels in the dashboard, in the center console or the like.
Control switches which are suitable for use in motor vehicles are known, for example, from DE 31 37 975 C2 or DE 195 48 216 A1. Such electrical switches have a contact system for switching an electrical voltage. The electrical voltage is applied to electrical connections, which lead to the contact system.
On the one hand, control switches are used which directly switch the voltage supply for the respective appliance to be switched in the motor vehicle. In this case, high currents of approximately 10 to 15 amperes may flow via the contact system of the switch for such appliances. For example, the voltage for the motor vehicle lighting headlights may be switched directly. Such switches must therefore be suitable for switching high power currents.
On the other hand, control switches are also increasingly being used to select individual functions in a controller which, for its part, then switches the corresponding electrical appliances. These switches are used to produce switching signals for which only low currents of about 10 milliamps flow. For example, this may be used to select the internal locking on the central locking system for the doors, or for controlling the vehicle computer etc. Such switches are thus designed to switch low signal currents.
Those switches which are designed for switching power currents are unsuitable for switching signal currents, and the converse is also true. Thus, until now, it has been necessary to provide different switch types in the motor vehicle, depending on the function. This increases stock-keeping costs, and complicates assembly, and it is impossible to preclude the possibility of assembly errors. In particular, control panels must be defined from the start with regard to what type of switch can be arranged at what point, so that a wide range of versions needs to be kept available, depending on the desired vehicle equipment.
The invention is based on the object of providing an electrical switch which has these different functional capabilities at the same time. In particular, the aim is to be able to switch a power and/or signal voltage in the motor vehicle using essentially one electrical switch type. In an extension, it is intended to simplify the formation of variants for control panels.
This object is achieved by the features of claim 1 for an electrical switch, and by the features of claim 9 for a switch arrangement.
The switch according to the invention has first electrical connections for supplying the contact system with a power voltage, as well as second electrical connections for supplying the contact system with a signal voltage. Optionally and if required, one connection can carry power current via the first electrical connections and/or signal current via the second electrical connections. Further refinements of the invention are the subject matter of the dependent claims.
For example, the operating member of the switch may be in the form of a rocker. For instance, two contact systems may be arranged in the housing of the switch. In the one, operated position, the rocker then acts on the one contact system in order to move it to the switched-on state. In the other, operated position the rocker moves the other contact system to the switched-on state. If desired, the one contact system may be used for switching the power voltage, and the other contact system for switching the signal voltage.
The switch housing may be mounted on a printed circuit board on which the supply lines for the signal voltage are located which, in turn, can optionally make contact with the second electrical connections of the switch. In the housing of the switch, the second electrical connections are preferably electrically connected to the contact system via a board. Lighting means for function and/or symbol lighting may also be arranged on the operating member on this board. The voltage for operation of the lighting means is likewise supplied via the second electrical connections.
The switching signals produced by the switch by means of the supplied signal voltage and corresponding to the switch position of the contact system can, according to one refinement, be transmitted via signal lines to a control circuit located on the printed circuit board. The switching signals can then be converted in the control circuit into bus signals, for example CAN bus signals, and can be transmitted to a bus line.
In one development, a holder which accommodates the first electrical connections is located on the lower face of the housing, in its central region, in such a manner that a plug can optionally be plugged on in order to supply the power voltage.
An opening which corresponds to the holder and whose shape and size allow the plug to pass through is in turn located in the printed circuit board. The second electrical connections are likewise located on the lower face of the housing. In particular, the second electrical connections are associated with the edge of the housing and are arranged adjacent to the holder. It is possible for the second electrical connections to be in the form of plug receptacles which are arranged in the form of a floating bearing with electrical connecting lines to the board in the housing of the switch. The second electrical connections can then be plugged onto associated plug contacts, which are located on the printed circuit board.
The contact system of the switch may be in the form of a snap-action system, which is known per se. In such a snap-action system, the operating member acts by means of an attachment on a bearing arm which is mounted on a connecting part such that it can move. The switching contact is in turn mounted in a blade bearing on the bearing arm such that it can move. A tension spring is attached on the one hand firmly in the housing and on the other hand in the switching contact, so that the switching contact interacts, with a switching action, with at least one fixed contact located on a further connecting part. If desired, there may also be two fixed contacts, between which the switching contact switches like a changeover switch. The connecting parts merge via an extension on one face into the first electrical connections. At least one connecting part leads via an extension on the other face to the board for the electrical connection to the second electrical connections.
The contact system of the switch is designed such that both the high power current and a low signal current can be switched. In one particular refinement of the invention, on the one hand the contact-making parts of the contact system, namely the switching contact and the fixed contact, are composed of a contact material that is suitable for power currents and, on the other hand, have a low electrical contact resistance. In order to reduce the contact resistance, it is possible to provide the contact-making parts with an electrically highly conductive layer, for example a gold layer or the like. In consequence, when the switch is used for switching signal currents, only a slight voltage drop occurs across the contact system. If necessary, when the switch is used for switching power currents, this layer may be destroyed or removed, with the voltage drop across the contact system being increased, although the functional capability of the switch is not adversely affected any more owing to the increased current density for power currents.
The switch according to the invention is used, in particular, in a switch arrangement for a control panel in a motor vehicle. In this case, a refinement of the switch is advantageous in which at least one resilient latching arm is arranged on the housing, so that the switch can be inserted in a clamped and/or locking manner into a supporting component. Conversely, the switch can be unlocked again and removed from the supporting component by applying a tool, a screwdriver or the like, to the latching arm. This tool has an arm, corresponding to the latching arm, for unlocking the latching arm, as well as an attachment which is connected to the arm for acting on the lower face of the housing. The switch can thus be pushed out of the supporting component on the side associated with the lower face of the housing.
In general, one control panel contains a plurality of such switches, which are each used for switching and/or initiating functions in the motor vehicle. In order to bring the control panel into use, and/or before the motor vehicle is brought into use, the control panel can be initialized by storing an assignment table in a storage device in the switch arrangement. The assignment table assigns each switch a function from the set of functions provided for the motor vehicle. The control circuit of the switching arrangement contains a processor, which is monitored by means of an external window watchdog module. Furthermore, the control circuit is provided with a voltage regulator assembly and is coupled to a bus system which is, for example, the CAN bus, by means of a high-speed transmission module as well as an upstream suppression inductor.
The control circuit uses the signals transmitted on the signal lines to detect the switching state of the respective switch in the switch arrangement. To this end, the control circuit can read the signal lines, for example by means of a multiplexing method, via analog/digital converters. On the basis of the assignment, stored in the storage device, for the respective operated switch, the control circuit then checks which function has been selected. If necessary, a bus signal which codes the respective function can then be generated in the control circuit, and this can be transmitted to the bus line. In order to minimize the current draw, the supply voltage for the electronic components of the switch arrangement can be switched to a sleep mode with a reduced current draw, and the signal voltage supply for the switches can be switched off.
The switches in the control panel often have function and/or symbol lighting, in which case the association between the function and/or symbol lighting and the respective switch is stored in the storage device during initialization. The function and/or symbol lighting can likewise be actuated by the control circuit and, if required, can also be dimmed by means of pulse-width modulation.
If the entire switch arrangement comprises a plurality of individual control panels, then the control panels may be independent from one another, and may each be in the form of a bus node. Each control panel is then initialized separately, using an assignment table. Furthermore, each control panel is connected to a bus line, and the information relating to the switching states of the switches arranged in the respective control panel is transmitted directly from the respective control panel to the bus line. In an alternative refinement, there is only one control panel, in the form of an independent master bus node, while the other control panels are in the form of slave bus nodes, which are dependent on the master bus node and have only basic functions of a bus node. The slave bus nodes transmit the information relating to the switching states of the switches arranged in the respective control panel via the bus line to the master bus node, without knowing the function of said information. The master bus node, which is initialized using an assignment table for all the control panels, then converts this received information into bus signals in accordance with the assignment table. In yet another refinement, the dependent control panels may also be in the form of only slave controllers without any bus function, in which case the slave controllers each have a serial interface. The slave controllers are connected to the master bus node by means of a serial data line, via the serial interfaces. The information relating to the switching states of the switches arranged in the respective control panel is then transmitted via the serial interface and the serial data line to the master bus node, which then converts this information into bus signals once again.
The advantages achieved by the invention are, in particular, that the electrical switch can be used universally. The appropriate plug just has to be plugged on to determine whether this is a load switch or a signal voltage switch. The switch may even be used as a load switch and as a signal voltage switch at the same time. This results in less stock-keeping, which in turn leads to cost savings. Furthermore, switch arrangements which use such switches can be designed more flexibly since the function associated with the respective switch does not need to be defined until the switch arrangement is initialized. Various versions of such control panels for motor vehicles can thus be kept in stock in modular form, at low cost, with the initialization for the respectively desired equipment variant being carried out only after being fitted in the motor vehicle. Furthermore, this also reduces the risk of incorrect items being fitted, thus leading to a considerable quality improvement.